Robots used to remove Fukushima’s highly radioactive used nuclear fuel, but they’re still problematic.

Plutonium problems won’t go away, By Chris Edwards, Engineering and Technology, February 15, 2022 ”’………………………………………At a conference organised by the International Federation of Robotics Research on the 10th anniversary of the accident, Toyota Research chief scientist Gill Pratt said the first robots “got there in the overhead luggage of commercial flights”. For all of them it was a baptism of fire.

Narrow staircases and rubble turned into insurmountable obstacles for some. Those that made it further failed after suffering too much radiation damage to key sensors and memories. Finally, some developed by the Chiba Institute of Technology were able to explore the upper floors of Reactor 2. The researchers designed their Quince to work for up to five hours in the presence of a cobalt-60 source that would generate an average dose of 40 grays per hour.

Direct radiation damage was not the only problem for the Fukushima robots. Reactors are protected by thick concrete walls. Wireless signals fade in and out and fibre-optic cabling becomes an impediment in the cluttered space of a damaged building.

To be close enough to the machines, operators had to wear bulky protective clothing that made teleoperation much harder than it would be in other environments. Several robots went into the building only to fail and get stuck, turning into obstacles for other machines.

The risk of these kinds of failure played into the nuclear industry’s long-term resistance to using robots for repair and decommissioning. Plant operators continued to favour mechanical manipulators operated by humans, separated by both protective clothing and thick lead-heavy glass.

Since Fukushima, attitudes to robots in the nuclear industry have changed, but remote control remains the main strategy. Pratt says humans remain generally better at control and are far better at dealing with the unstructured environments within many older and sometimes damaged installations.

The long-term aim of those working on these systems is to provide robots with greater degrees of autonomy over time. For example, surveillance drones will be flown with operator supervision but the machines are acquiring more intelligence to let them avoid obstacles so they need only respond to simpler, high-level commands. This can overcome one of the problems created by intermittent communications. One instance of this approach was shown when UK-based Createc Robotics recently deployed a drone at Chernobyl and Fukushima, choosing in the latter case to survey the partly collapsed turbine hall for a test of its semi-autonomous mapping techniques.

To get more robots into play in the UK, the NDA has focused its procurement more heavily on universities and smaller specialist companies, some of which are adapting technologies from the oil and gas industry.

The NDA expects it will take many years to develop effective robot decommissioning and handling technologies. It has put together a broad roadmap that currently extends to 2040. Radiation susceptibility remains an issue. Visual sensors are highly susceptible to damage by ionising radiation. However, a mixture of smarter control systems and redundancy should make it possible to at least move robots to a safe point for repair should they start to show signs of failure.

Another design strategy being pursued both in the UK and Japan is to build robots as though they are a moving, smart Swiss-army knife: armed with a variety of detachable limbs and subsystems so they can adapt to conditions and possibly even perform some on-the-fly repairs to themselves.

Slowly, the technology is appearing that can handle and at least put the waste out of harm’s way for a long time, though you might wonder why the process has taken decades to get to this stage of development. ……………. (Goes on to laser developments, again, far from a sure thing.) https://eandt.theiet.org/content/articles/2022/02/plutonium-problems-won-t-go-away/